I think it's more of a money thing. Basically every English club that makes the champions league is earning more than most other teams in the tournament, now that theres some decent managers in the mix as well, I don't think it'll be an uncommon sight to see English teams getting further more consistently.
The money thing has been going on for decades now, I don't think it has anything to do with how English teams perform. During the period of 2012-2017 English teams were also making more money than their European counterparts but went through their worst people in the UCL and Europa League.
What has made a bigger difference to me is luck for one, Spurs needed Inter to not win at home against PSV while Chelsea needed penalties to beat Frankfurt, but more than that are the managers, which are of higher quality than before. City have Pep compared to Mancini/Pelligrini, Liverpool have Klopp, Spurs have Pochettino. These are the top 3 managers in the world for me and their impact on the team is showing through their success.
For the future, I actually doubt whether
all English teams will be able to dominate. I think we'l see a similar situation to the La Liga where Barca and Real dominated domestically and in Europe; right now both Liverpool and City are head and shoulders above their domestic competition while also being amongst the best in Europe. The issue is with Chelsea, Spurs, Arsenal and United.
- Chelsea are going to lose Hazard and the transfer ban means they won't be able to upgrade their squad, which has a big hole in the striker position. Therefore next year will be very tough for them because I don't think they can compete at the highest level with their current squad ( minus Hazard, plus Pulisic).
- Spurs look likely to lose Kane and Eriksen in the summer. I know that is said every transfer window but with Madrid looking likely to invest heavily in their squad, those two names maybe front on their list. Poch might stay but I think their squad will suffer a dip or they will have to sign many players and it may take them time to gel.
- Arsenal are in disarray with regards to their squad quality and the lack of investment coming in from Kronke. It is being said that Emery will only have 40 MP to invest and that surely will not be enough for them to compete in the Champions League.
With this, as will see Barca, Real and Bayern invest heavily to improve their squads so we can expect their performances to improve come next season. Liverpool and City though I still think will be in the latter stages of the UCL for the next few seasons.